Prion is a protein-based infectious agent that causes a group of neurodegenerative disorders known as transmissible spongiform encephalopathies (or prion diseases). Despite years of researches, the molecular mechanism of prion transmission remains unclear. The recently developed protein misfolding cyclic amplification (PMCA) protocol for generating highly infectious prions from bacterially expressed recombinant prion protein in the presence of well-defined cofactors offers unique opportunities to probe the molecular basis of prion transmission. In this multiple PI application, we propose to use an integrated approach combining generation of recombinant prions in vitro, animal bioassay, and biophysical/structural characterization to (i) elucidate the role of lipids in prion infectivity, (i) rigorously test the hypothesis that a strong prion transmission barrier can be abrogated by serial adaptive conformational changes, and (iii) establish a novel recombinant prion propagation protocol to generate large quantities of infectious prions and, thus, facilitate future structural studies at a higher resolution level. These studies, which integrate structural and biological characterization of recombinant prions, are expected to provide valuable insights into the mechanism of prion transmission. Moreover, given the recent discoveries of a prion-like propagation of ordered protein aggregates in neurodegenerative disorders, such as Alzheimer's and Parkinson's diseases, the findings from our studies should also have important implications for understanding the pathogenic process in these more common neurodegenerative diseases.